even after playing it i still dont understand what a theramin is supposed to do

Playing a theramin or playing strongbad?

edit: It's hard to explain, but here's my shot at it.

Theramin: Basically a box with a wire/antenna poking out the top. When you move your hand towards the wire it will make a noise, depending on how close, and how high or low on the wire you are. Higher is higher pitch, lower on wire makes lower pitch. The closer your hand the louder, and also effectes the pitch in a way. Then there's something else on the box that does basically the same thing, changes the sound, also, according to where your hand is placed. You never actually touch the instrument though.

You can hear a theremin as the lead instrument through most of the track "The Black Hole" in Sam & Max Season One's soundtrack. It's the instrument which sounds sort of like a synthesized version of a woman singing... sort of? You can hear it the most obviously starting around 1:26 in that track.